Fuel injection control system

ABSTRACT

An internal combustion engine fuel injection control system of the type having one or more electrically controlled fuel injector valves which are opened and closed as a function of rotation of each revolution of the crank shaft and/or the pressure in the engine intake manifold so that the open time of the fuel injector valves changes with variations in the speed of the crank shaft even if the pressure in the engine intake manifold remains constant. This is accomplished by a control circuit that produces a periodic signal having periods and signal durations which are dependent upon the time required for the crank shaft to complete one revolution. Each signal generated during a revolution of the crank shaft includes a portion wherein the magnitude of the signal increases at a constant rate. The constant rate at which the magnitude of the periodic signal increases remains the same regardless of the changes in the duration of the periodic signal.

United States Patent 1191 R ddy May 22, 1973 [54] FUEL INJECTION CONTROL SYSTEM Primary ExaminerLaurence M. Goodridge Assistant ExaminerCort R. Flint 75 In entor: unuthula N. R dd H h d 1 v I e arse ea Attorney-Raymond J. Eifler and Plante, Hartz, Smith & Thompson [73] Assignee: The Bendix Corporation, Southfield,

Mich. [57] ABSTRACT [22] Filed: Dec. 28, 1970 An internal combustion engine fuel injection control system of the type having one or more electrically [21] 101896 controlled fuel injector valves which are opened and closed as a function of rotation of each revolution of [52] US. Cl. ..l23/32 EA, 123/119 R the crank shaft and/or the pressure in the engine in- [51] Int. Cl. ..F02d 5/00, F02m 51/00 take manifold so that the open time of the fuel injec- [58] Field of Search ..l23/32 EA tor valves changes with variations: in the speed of the crank shaft even if the pressure in the engine intake [56] References Cited manifold remains constant. Thisis accomplished by a control circuit that produces a periodic signal having UNITED STATES PATENTS periods and signal durations which are dependent 3,240,191 3/1966 Wallis ..123/32 EA "P the time required the crank Shaft to complete 3,314,407 4/1967 Schneider ..l23/l48 B one revolution Each Signal generated during a revolu- 3,456,628 7/1969 Bassot et al. 123/32 EA tion of the crank shaft includes a portion wherein the 3,464,396 9/1969 Scholl ..123/32 EA magnitude of the signal increases at a constant rate.

3,645,240 2/1972 Monpetit ..123/32 EA The constant rate at which the magnitude of the 3,653,365 p i EA periodic signal increases remains the same regardless 3,651,343 3/ 1972 p r 123/32 EA of the changes in the duration of the periodic signal. 3,659,571 5/1972 Lang ..l23/32 EA 20 Claims, 7 Drawing Figures rmcesn PULSES TRIGGER 1 PULSES DELAY PULSES CAPACITOR vomcs CAPACITOR VOLTAGE COMPARATOR L OUTPUT PULSES was, L

IIIY22I9I5 3,734,068

SHEET 1 OF 4 FUEL INJECTION CONTROL CIRCUITRY FUEL INJECTORS RPM PREssuRE 3/ ENGINE SENSOR 5 SENSOR MANIFOLD 7 FIGURE 1 SIGNAL FROM 3 CHARGING ENGINE RPM TRANSDUCER C'RCU'TRY H TRI TRIGGER PULSE ELECTRONIC FORMING NETWORK SWWCHING pg NETWORK TRZl lTRI #1 DELAY 1 1 1 21M PULSE Cll I I C2 1 CAPACITOR NETWORK g E vCI c2 VCI v02 (T2) T2 (TI) (TI) ELECTRONIC SWITCHING NETWORK VCI v (T2) ELECTRONIC I I SWITCHING SIGNAL FROMI NETWORK W2 COMPARATOR MANIFOLD PRESSURE 3 4- TRANSDUCER l l 10 INVENTOR. GP2 GPI FIGURE 2 JUNUTHULA N. REDDY ATTORNEY PATENIE saw 2 21975 SHEET h 0F 4 OP IUPISm U ZOE..-.UM M QUZCI OP PRESS URE FGURE 7 INVENTOR.

JUNUTHULA N. REDDY my A TTORN EY 1 FUEL INJECTION CONTROL SYSTEM BACKGROUND OF THE INVENTION this operated This invention relates to an internal combustion fuel injection control system of the type having a control circuit to electrically control the open time of an electromagnetically operated fuel injection valve in response to the rotation of the engine crank shaft and/or the pressure in the engine intake manifold. The invention is more particularly related to an improved fuel injection control system that produces control pulses having durations which are a function of engine cycle, an engine cycle being the time required for each cylinder to complete one operating cycle.

Basically, an electrically controlled fuel injection system for an internal combustion engine includes devices for sensing one or more operating parameters of the engine and a control circuit that controls the amount of fuel to the engine in response to the operating parameters sensed. The output of the control circuit is generally in the form of pulses which are applied to electrically controlled fuel injector valves so that the open time of the valves, which inject fuel into the engine cylinder, is determined by the duration of the pulses which are functions of one or more operating parameters of the engine. Therefore, the pulse time, and hence the period during which fuel is injected, which may be termed the injection time, can be made dependent on various operating conditions or parameters of the engine, for example: vacuum or absolute pressure in the intake manifold; the speed of the engine; and engine temperature. Otheroperating conditions of the engine in a prime mover system can also be considered, for example: voltage of the vehicle battery; or special components of the start up system. In any event, no matter what parameter is chosen to control open time of the fuel injection, the time during which fuel is injected into the engine should be so chosen that the system is optimized under all operating conditions. Thus, best fuel economy can be obtained regardless of the speed of the engine or the load placed thereon; further, pollution caused by exhaust gases from the engine will be minimized since incomplete combustion can be avoided.

Presently, rpm information for fuel injection control circuitry is gathered by integration and used to gener ate pulseswhich are also a function of pressure. However, a close look at engine requirements reveals that the duration of the pulses applied to the fuel injector valves should be able to vary with changes in time for each revolution of the engine crank shaft and that the change in pulse durations be independent of the magnitude of the pressure in the engine intake manifold.

SUMMARY OF THE INVENTION This invention provides an electronic fuel injection control system with the capability of changing the open time of the associated fuel injection valves as a function of each revolution of the engine crank shaft, such change being independent of the engine intake manifold pressure.

The invention comprises an internal combustion engine fuel injection fuel control system characterized by a control circuit which produces a pulse train having periods and pulse durations which are functions of each cycle of the engine and are capable of varying the open time of a fuel injection valve or valves independently of the magnitude of the pressure in the engine intake manifold.

In one embodiment of the invention, the open time of an electromagnetically operated fuel injection valve is controlled by a circuit which comprises: means for generating a signal which is a function of the engine manifold pressure; means for generating a periodic signal having periods and signal durations which are functions of each revolution of the engine crank shaft; means for comparing the pressure signal to the periodic signal and producing a resultant periodic signal having signal durations which are functions of each revolution of the engine crank shaft and the engine intake manifold pressure; and means for applying the resultant periodic signal to the electromagnetically operated fuel injection valve to change the open time of the fuel injection valve in response to a change in the rotational speed of the crank shaft when the pressure in the intake manifold remains constant. In other words, a change in the duration of a control pulse (APW) may be expressed as a function of manifold pressure (MP) and engine speed (RPM) as follows:

APW =f(AMP) +f(ARPM) +f(AMP, ARPM) and when manifold pressure remains: constant and RPM changes, the change in the duration of the control pulse is reduced to the following:

APW f (ARPM) Accordingly, it is an object of t.-is invention to optimize the open time of electromagnetically opeated fuel injection valves at all engine speeds.

It is another object of this invention to improve the response time of a fuel injection control system so that it responds to changes in the speed of each revolution of the crank shaft even when the pressure in the intake manifold remains constant.

It is still another object of this invention to improve the control of fuel injection valves to obtain better airto-fuel mixtures.

It is a further object of this invention to make the pulses applied to the fuel injection valve independent functions of the intake manifold pressure of the engine and the speed of the engine.

The above and other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings and claims which form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a fuel injection control system.

FIG. 2 is a block diagram of a. control circuit for a fuel injection control system which utilizes the principles of this invention.

FIG. 3 is a timing diagram which illustrates the various wave forms of the control circuit shown in FIG. 2.

FIG. 4 is an illustration of the voltage signals applied to the comparator at various speeds for a constant engine intake manifold pressure.

FIG. 5 is a comparison of the comparator output pulses for increasing engine speeds.

FIG. 6 is an illustration of some possible variations of the wave forms that represent the speed of the engine.

FIG. 7 is a schematic diagram of the control circuit block shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, FIG. 1 illustrates a control system for an internal combustion engine 7 wherein the control circuitry l obtains its control signals from sensors 3, to control the operation of the fuel injectors 2.

The sensors 3 and 5 include one or more devices for sensing rotation of the engine crank shaft and the pressure in the engine intake manifold.

The fuel injectors 2 are comprised of electromagnetically operated fuel injection valves which are generally located immediately adjacent the inlet valve to the engine cylinders (not shown). Fuel is supplied under pressure to each of the injector valves so that when a valve is opened fuel will be injected into a cylinder of the engine 7.

FIG. 2 is a block diagram which illustrates how the control circuitry reacts to trigger pulses TR] and TR2 which are synchronized with the rotation of the engine crank shaft to open each group of fuel injector valves at the proper time.

Trigger pulse TRl initiates the pulse that opens the fuel injector valve or valves in group 1 and trigger pulse TR2 initiates the pulse that opens the fuel injector valve or valves in group 2, thus completing one engine cycle. The heavier lines in the drawing indicate the signals that are present when the trigger pulse TR2 is present. The lighter lines on the drawing indicate the signals that are present when the trigger pulse TRl is present.

The control circuitry includes a charging circuit a first electronic switching network a trigger pulse forming network a capacitor network a delay pulse network 50; a second electronic switching network 60; a third electronic switching network 70; and a comparator 80.

The charging circuitry 10 includes two constant current sources which supply different currents I, and 1 to the first electronic switching network 20, the magnitude of the constant current sources I, and I, being such that I is capable of charging a capacitor to a higher voltage than I,. Preferably, the charging rate from current source I is greater than from current source I,.

The trigger pulse forming network 30 and the pulse delay network 50 supply pulses to the first electronic switching network 20. The output of the first electronic switching network 20 is connected to the capacitor network 40 which includes capacitors Cl and C2. During the presence of a trigger pulse (TRl or TR2) the currents I, and I are applied to the capacitors C1 and C2. Trigger pulse TR2 causes the first electronic switching network 20 to apply current I to capacitor C1 and current I, to capacitor C2. Trigger pulse TRl causes the first electronic switching network 20 to apply current I, to capacitor C1 and current I to capacitor C2. The delay pulses P1 and P2 applied to the electronic switching network 20 delay the application of the current I, to capacitors C1 and C2 for a predetermined amount of time to obtain a predetermined wave shape. The output of the capacitor network is the voltages created across the capacitor C 1 and C2 during the application of the currents I, and I, to the capacitor C1 and C2. During the time period T1 when there is a trigger pulse TRl present, the output voltage across C1 will be a function of current I, and the output voltage of C2 will be a function of 1 During the time period T2 when trigger pulses TR2 are present, the voltage across capacitor C1 will be a function of current 1 and the voltage across capacitor C2 will be a function of current I,.

The electronic switching network 60 receives the voltages from the capacitor C1 and C2 and produces an output which is the voltage across capacitor C1 during the time period T2 when current 1 is applied to capacitor C1 and the voltage across capacitor C2 during the time period T1 when the current 1 is applied to the capacitor C2.

The comparator 80 receives each capacitor voltage during a different time interval T1 and T2 and compares it with a signal from the sensing device 5 which monitors the pressure in the engine intake manifold. The comparator 80 then produces output pulses which have durations which are a function of both the intake manifold pressure and/or the rotation of the crank shaft of the engine and will vary in duration if either the intake pressure varies or the rotation of the engine crank shaft varies. In situations where the pressure in the intake manifold remains constant but the rotation of crank shaft varies, the duration of the pulses leaving the comparator will vary accordingly.

The third electronic switching network receives the output pulses from the comparator and synchronizes, with the rotation of the crank shaft, their application to the injector valves.

FIG. 3 is a timing diagram which illustrates graphically the inputs and signals of the fuel injection circuitry shown in FIGS. 2 and 7.

The trigger pulse trains u, and u are comprised of a series of pulses having durations TR] and TR2 which can vary in duration as a function of rotation of the engine cam or crank shaft. As the rotation of the crank shaft increases, the duration of the pulses TRl and TR2 decreases. The time P corresponds to the time required for l revolution of the engine cam shaft and is equal to the total consecutive time interval of TRl TR2.

The pulse trains u and u, are the delay pulses which are applied to the electronic switching network 20 shown in FIG. 2 and are synchronized with the leading edge of a corresponding trigger pulse so that the repetition rate of each pulse train a u, is dependent upon the corresponding repetition rate of trigger pulse trains u and u Pulse trains a and u represent the voltages generated across capacitors C1 and C2 respectively. During the time period T1 the current I is supplied to capacitor Cl and the current I is supplied to capacitor C2. However, a delay pulse Pl delays the application of the current I, to CI for a predetermined time interval. The points A to B indicate the time interval when no current is being supplied to the capacitor C1; the points B to C indicate the time duration that capacitor C1 is being charged by current I,; and the points C to D indicate the time period that the capacitor C1 has been fully charged by the current I,. The time period T2 indicates the time interval that the current I is supplied to Cl and the current I, is supplied to C2. During this time interval T2, the delay pulse P2 prevents the current I, from charging capacitor C2 for a predetermined time interval. From the points A to B no current from I, is supplied to capacitor C2. From the points B to C the current I, is charging capacitor C2. From the points C to D capacitor C2 has been fully charged by current I, and remains at a constant value. Between the points D and E the current I, is charging capacitor C1, the constant current source being such that the capacitor C1 does not reach a steady state value below a predetermined value.

An important aspect of the invention is the shape of pulse trains 14 and a between points A and D and A and D which establishes the locus of starting points for ramp voltage D to E and D to E. The slope of the lines from D to E and from D to E remains the same for each period regardless of changes in the duration of T1 and T2. The ramp thus generated is distinguishable from a saw tooth wave which would change its slope if its duration changed.

It can be seen from pulse trains u and u that as the durations of the signal decrease the predetermined shape of the signal between points A and D changes its configuration, whereas the configuration of the signal between points D and E remains the same.

Pulse trains u and u together indicate the duration of the comparator output pulses in the absence of any change in the pressure in the engine intake manifold. The pulse trains u and a, have a repetition rate dependent upon the trigger pulse trains u and u and in the instance where the intake manifold pressure is constant, the duration of the output pulse may vary if the speed of the engine (crank shaft) varies. The duration of each pulse W1, W3, W5, W7, W9, etc. of pulse train u begins when the current I is applied to capacitor C2 and ends when the voltage reaches a predetermined value F established by the comparator 80. Similarly, the duration of each pulse W2, W4, W6, W8, etc. of pulse train u begins when the current I, is applied to capacitor C1 and ends when the voltage reaches a predetermined value F established by the comparator 80.

Since RPM correction is not required for all engine speeds the duration of the output pulses is programmed to increase for predetermined engine speeds only. This is accomplished by shaping the voltage wave (A to D; D to E; A'to D and D to E) of the capacitors Cl and C2.

Consider now the pulses W1, W2, W3, W4, W5, W6, and W7 which have the same duration because the initial magnitude (lines C D and CD) at which the corre sponding ramp voltage (D E and DE) begins is the same and the magnitude F and F is the same. However, output pulses W8 and W9 are of a longer duration than preceding pulses since the ramps D E and DE' begin at some point along line B C and BC which is below the magnitude at C and C. In other words, since the current I, supplied to capacitors C1 and C2 begins at a lower initial value it takes a longer time interval W8 and W9 (D to F and D to F) to reach a predetermined value (F and F).

An important distinction between the prior art and this invention is the'fact that pulse trains u and u, are not pulse trains having a constant period and duration because the pulse (W1 and W2, etc.) are not always identical in duration and because the repetition rate P is not a regular interval but varies with a change in the speed of each revolution of the crank shaft.

FIG. 4 is a graphical illustration of the pressure signal P to the comparator (FIG. 3, 80), which is an indication of the pressure in the engine intake manifold and the voltage generated across one of the capacitors (C1, C2) for a time interval (T1 T2) which is equal to the time required for the engine crank shaft to complete 1 revolution.

In a preferred embodiment of the invention the time required for the engine crank shaft to complete 1 revolution (cycle) is divided into 2 equal parts (T1 and T2). During the first half of the cycle there is a predetermined time delay (line AB) before the current I is applied to a capacitor. Since the current I, is from a constant current source, the capacitor charges in the manner shown (line BC). The voltage reaches a maximum value line CD) after the time interval BC passes. Although both the shape and maximum value of line BC is predetermined by the circuit shown in FIG. 7, the components of the circuit may be arranged and/or changed to obtain any desired shape and maximum value. During the second half of the cycle, current 1 is applied to the capacitor to obtain the ramp voltage shown by line DE. Since current I is from a constant current source, the capacitor is charged at the same rate each time the capacitor is charged by current I As the engine speed increases, the time intervals T1 and T2 decrease by equal amounts. This shortens the first half cycle (Til) that determines the time during which current I, is supplied to the capacitor. Similarly, the second half cycle T2 that determines the duration in which current I, is supplied to the capacitor is shortened. This is illustrated by dotted lines 2, 3 and 4 which have the same slopes as line 1 but begin at a point in time before line 1 (DE).

The comparator output pulse width W1 is the interval D to P which is from the time (D) that the current I, is applied to a capacitor until the voltage on the capacitor reaches a predetermined level (F), which is established by the pressure in the engine intake manifold. Returning now to dotted lines 2, 3, and 4 representing progressively increasing engine speeds, it is apparent that pulse width W2 generated by line 2 is the same duration as pulse Wl since the initial magnitude of the starting point of the ramp is the same. However, since the initial magnitude of line 3 is below that of line 2, it takes a longer time for the capacitor voltage to reach the same level F as line 1 and 2. Therefore, the pulse width W3 is greater than W1 and W2. Similarly, pulse width W4 is greater than pulse width W3. For purposes of clarity, the pressure P in the intake manifold was considered to remain constant while the engine speed was considered to be changing, as indicated by dotted lines 2, 3, and 4. In actual practice there are an infinite number of lines parallel to the line P that may represent the pressure in the engine intake manifold. However, to emphasize an object of this invention to obtain a correction in the output pulse width. for a change in the speed of the engine when there is no change in the pressure in the engine intake manifold -the pressure signal is shown as constant.

FIG. 5 compares the durations of some of the comparator output pulses W1, W2, W3, and W4 for engine speeds related to lines 1, 2, 3, and 4 in FIGQ4.

FIG. 6 indicates some of the possible variations in the wave form A to E which may be obtained by switching different current sources to one or more capacitors through different components. For instance, line BC in the preferred embodiment. is linear, although it could be non-linear as shown by the dotted lines 10, 12 or a series of small steps. Similarly, line DE in the preferred embodiment is linear l and has a particular slope which may be varied as shown by dotted line 5. Lines 15 and 117 represent 2 of the many possible pressure signals fed into the comparator to establish the termi' nation points (F) of comparator output pulses.

FIG. 7 is a schematic diagram illustrating a preferred arrangement for obtaining the function of the control circuitry shown in FIG. 2.

The components of the charging circuitry have been enclosed by broken lines and include the voltage source 100; transistors 101 and 102; resistors 110 through 115. The output of the transistorslOl and 102 are the currents I and I which are the constant currents for charging the capacitors Cl and C2.

The components of the first electronic switching network are also enclosed by dotted lines. The first electronic switching network 20 includes transistors 131 through 138; resistors 141 through 148; and diodes 151 through 160. The currents I and I from the charging circuitry 10 are introduced into the first electronic switching network 20 at the collectors of transistors 131 through 134. The currents I and I are then switched between transistors by the application of the trigger pulses TRl and TR2 to the base of the transistors 131 through 134 through resistors 141 through 144. This action causes the currents I and I to alternately charge capacitors C1 and C2.

The capacitor network 40 comprises two capacitors Cl and C2 which are alternately charged by currents I and I in response to trigger pulses TRl and TR2.

The second electronic switching circuit 60 is comprised of two diodes 161 and 162 which are alternately forward and reverse biased by the voltages on capacitor C1 and C2 and supply the periodic signals to the comparator 80.

The comparator 80 is shown in the lower right hand portion of FIG. 7 and is encompassed by dotted lines. The comparator 80 comprises transistors 171, 172, 173; resistors 181, 182, 183. The comparator 80 receives an input signal from the engine intake manifold at the base of transistor 172 and the periodic signals generated by the capacitors Cl and C2 at the base of transistor 171. The signal from the engine intake manifold establishes the reference voltage that causes the termination of an input pulse (u a when a capacitor voltage (u u reaches that voltage (F and F). The output then of the comparator 80 is a series of pulses which can be taken from the junction between resistors 182 and 183. The output pulses, therefore, have durations which vary with changes in the intake manifold pressure and/or changes in the revolution rate of the engine crank shaft.

The wave forms 14,, u u 14,, u 14 u and 14 shown in FIG. 3 have been indicated on the schematic of FIG. 7. For instance, the output of the comparator 80 which goes to the third electronic switch 70 is shown to be the pulse trains u and 14 Similarly, pulse trains of 14, and u are shown at the inputs to the second electronic switching circuits 60. The pulse trains u,, u 14 and a are shown as the inputs to the first electronic switching network 20. At this point, it should again bemphasized that the pulse widths W9 and W8 of the pulse trains u and u (FIG. 3) are of a duration greater than the preceding pulse W1, W2, etc. This is because the ramp portions DE and DE' of pulse trains a and u begin at a point in time on the slope of line BC and B'C'. Since the slope of the ramps D E and D'E' remains the same for all cycles and the ramps D E and D'E' start at a lower initial value for W8 and W9, it takes a longer time interval for the ramp to reach the predetermined value F and F, making the durations of W8 and W9 longer than a corresponding preceding pulse.

OPERATION Referring now to the drawings, the control system operates as follows: The sensing device 3 which senses the rotation of the engine and the sensing device 5 which senses the pressure in the intake manifold of the engine transmit signals to the control circuitry 1. The signal from the rpm sensor 3 is introduced into a trigger pulse network 30 whose outputs are connected to electronic switching networks 20, 30 and to synchronize the application of voltage'pulses to the fuel injection valves with the rotation of the engine. The control circuitry includes two constant current sources which are alternately applied to capacitors Cl and C2 in response to the trigger pulses generated by the pulse forming network 30. The capacitors Cl and C2 are then periodically charged to the voltages shown in FIG. 3 on u and 14 The second electronic switching circuit 60 then transmits the voltage generated across capacitor CI for the period T2 and the voltage generated across capacitor C2 for the period T1 to the comparator which also receives a signal indicative of the intake manifold pressure. The signal indicative of the intake manifold pressure establishes a reference voltage level which, when reached by the capacitor voltage u and u terminates a pulse (W1, W2, etc.) leaving the comparator 80. The comparator 80, therefore, produces pulse trains u and u which have pulses having durations which are a function of the engine intake manifold pressure and/or the speed of the engine. Therefore, the durations of the pulses (W1, W2, etc.) from the comparator 80 will change if either the speed of the engine or the pressure in the intake manifold increases or decreases. More importantly, the duration of the pulses applied to the fuel injector valves may vary when the rotational speed of the engine crank shaft varies even though the pressure in the intake manifold remains constant.

After leaving the comparator 80, the output pulses are then introduced into a third electronic switching network 70 which synchronizes the application of these pulses with the rotation of the engine crank shaft.

Therefore, the pulses controlling the open time of the fuel injection valves will vary in duration if the time required for one revolution of the engine crank shaft varies. This fast response time, heretobefore unattainable, optimizes the air-to-fuel ratio during operation of the engine, thereby maximizing the performance of the engine and decreasing the pollutants which would normally be exhausted into the atmosphere.

While a preferred embodiment of the invention has been disclosed, it will be apparent to those skilled in the art that changes may be made to the invention as set forth in the appended claims, and, in some cases, certain features of the invention may be used to advantage without corresponding use of other features. For example, the magnitudes, durations and polarities of the pulses shown in the diagrams may be varied in different ways to achieve the objects of the invention. For instance, the shape of the voltage across capacitors C1 and C2 (FIG. 3) from A to D and A to D may be changed to any desired configuration by proper selection of components in the charging circuit 10. Further, the circuitry may be modified so that more than two groups of injector valves can be controlled or more than two constant current sources may be used to obtain the desired wave forms. Also, the slopes of the ramp voltages generated at the capacitors Cl and C2 can be tailor-made for different types of engines so that the open time of the injector valves which is a function of the speed of the engine will more closely match the engine requirements. Accordingly, it is intended that the illustrative and descriptive materials herein be used to illustrate the principles of the invention and not to limit the scope thereof.

Having described the invention, what is claimed is:

1. In combination with an internal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of at least one fuel injection valve in response ro the rotation of an engine crank shaft, the improvement wherein said control circuit comprises:

means for generating a first pulse train which produces at least one pulse for each revolution of the engine crank shaft, said first pulse train having pulses which begin at an initial point and then increase at a controllable rate;

means for varying the magnitude of the initial point at which each of said pulses of said firstpulse train begin;

means for generating a second pulse train having pulse durations which begin when a pulse from said first pulse train is initiated and end when a pulse from said first pulse train reaches a value established by a sensed engine operating parameter; and

means for applying the pulses of said second pulse train to the fuel injector valve to open the valve for the duration of a pulse of said second pulse train.

2. The combination as recited in claim 1 wherein the means for varying the magnitude of said initial point at which each of said pulses of said first pulse train begins comprises:

a ramp generator which establishes a locus of points at which the pulses of said first pulse train are capable of beginning; and

means for delaying the generation of said ramp for a predetermined time interval.

3. In combination with an intemal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of at least one fuel injection valve in response to the rotation of an engine crank shaft, the improvement wherein said control circuit comprises:

means for generating a first pulse train which produces a pulse for each revolution of the engine crank shaft, said first pulse train having pulses whose magnitudes vary in a predetermined manner;

means for generating a second pulse train which produces a pulse for each revolution of the engine crank shaft out of phase by a known phase differential with the pulses of said first pulse train, said second pulse train having pulses whose magnitudes increase at a predetermined rate;

means for combining the pulses of said first and second pulse trains so that the beginning of a pulse from said second pulse train terminates a pulse from said first pulse train and the end of a pulse from said second pulse train initiates a pulse from said first pulse train;

means for generating a third pulse train having pulses which begin when a pulse from said second pulse train begins and end when a pulse from said second pulse train reaches a predeterminable value; means for applying said third pulse train to the fuel injection valve to open the valve for the duration of a pulse from said third pulse train.

4. The combination as recited in claim 3 wherein said means for generating a third pulse train includes:

means for generating a signal which is a function of an operating parameter of the engine to establish said predeterminable value which when reached by each of said pulse of said second pulse train, terminates a third pulse train pulses.

5. The combination as recited in. claim 4 wherein the duration of a pulse of said first and second pulse train is equal to the time required for the said engine to complete one engine cycle.

6. In an internal combustion engine fuel control system of the type having triggering means operative to generate triggering signals indicative of the occurrence of engine triggering events, a computing means comprising:

at least two current source means operative to generate first and second electrical currents having predeterminable magnitudes; network means, having at least one storage member, for receiving said currents and storing electrical signals in response thereto;

first switching means for sequentially applying said currents to said at least one storage member in response to the triggering signals, said first current being applied to said at least one storage member for a period of time immediately following a first triggering signal and said second current being applied to said at least one storage member in response to a selected succeeding triggering signal; and

threshold means coupled to said network means responsive to the electrical signal stored therein operative to generate a signal for the period of time following the selected succeeding triggering signal that the stored electrical signal maintains a selected relationship to a threshold value.

7. The system as claimed in claim 6 wherein said net- 45 work means comprise:

at least two capacitive members and said first switching means are operative to alternating apply each of said first and second currents to said two capacitive members whereby the charge accumulated on said capacitive members will be a function of the duration of application of each of said first and second currents.

8. The system as claimed inclairm 7 wherein said second current can charge either of said at least two capacitors to a higher voltage.

9. The system as claimed in claim 7 wherein said at least two capacitors are substantially equal.

10. The system as claimed in claim 6 including further second switching means responsive to a first triggering event operative to controllably limit the maximum value of electrical signal stored by said storage member. I

11. The system as claimed in claim 10 wherein said second switching means further include means responsive to the, time elapsed from said first triggering signal operative to controllably vary the limit established by said second switching means.

12. The system as claimed by claim wherein the limit value of stored electrical signal is removed upon the occurrence of the selected succeeding triggering event.

13. In combination with an internal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of an electromagnetically operated fuel injection valve in response to the rotation of said engine crank shaft, the improvement wherein said control circuit comprises:

means for generating a first pulse train which produces a pulse for each revolution of said engine crank shaft, said first pulse train having pulses which begin at an initial point and then increase at a constant rate which rate is the same for each of said pulses;

means for varying the magnitude of the initial point at which each of said pulses of said first pulse train begin;

means for generating a second pulse train having pulse durations which begin when a pulse from said first pulse train is initiated and end when a pulse from said first pulse train reaches a predetermined value established by a sensed engine operating parameter; and

means for applying the pulses of said second pulse train to said electromagnetically operated fuel injector valve to open said valve for the duration of each pulse of said second pulse train. 14. In combination with an internal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of an electromagnetically operated fuel injection valve in response to the rotation of said engine crank shaft, the improvement wherein said control circuit comprises:

means for generating a first pulse train which produces a pulse for each revolution of said engine crank shaft, said first pulse train having pulses whose magnitudes vary in a predetermined manner; means for generating a second pulse train which produces a pulse for each revolution of said engine crank shaft 180 out of phase with the pulses of said first pulse train, said second pulse train having pulses whose magnitudes increase at a constant rate for all pulse durations; means for combining the pulses of said first and second pulse trains so that the beginning of a pulse from said second pulse train terminates a pulse from said first pulse train and the end of a pulse from said second pulse train initiates a pulse from said first pulse train; means for generating a third pulse train having pulses which begin when a pulse from said second pulse train begins and ends when a pulse from said second pulse train reaches a predetermined value; and

means for applying said third pulse train to said electromagnetically operated fuel injection valve to open said injector valve for the duration of each pulse from said third pulse train.

15. A fuel injection control system responsive to at least two variable operating characteristics of an internal combustion engine for controlling the provision of fuel to said engine comprising:

means responsive to one of the variable operating characteristics for generating a threshold signal having a value determined by the value of said one variable operating characteristic;

means for generating a cyclic signal having a value that varies at a predetermined rate from an initial value to the threshold value at least once during each cycle of engine operation; and

means responsive to the other variable operating characteristic for changing said initial value, a change in either the initial or threshold value thereby changing the time required for the cyclic signal to reach the threshold value by an amount that is independent of the magnitude of the other of said values;

fuel delivery means responsive to said cyclic signal for providing fuel to the engine for a period in each engine cycle determined by the time required for said cyclic signal to vary from said initial value to said threshold value.

16. The control system of claim 15 in which:

said threshold signal generating means comprise means responsive to engine air consumption; and

said means for changing said initial value comprise means responsive to engine speed.

17. The control system of claim 15 in which said means for generating a cyclic signal comprises means for generating a signal that varies at a fixed rate, a change in either one of said initial or threshold values thereby changing the period of fuel injection by the same amount for all levels of the other of said initial or threshold values.

18. The control system of claim 15 in which said means for generating said cyclic signal comprise:

means for receiving and storing electric signals;

a first current source for charging said receiving and storing means to the threshold value; and

means for discharging said receiving and storing means at least once for each engine cycle, the charging of said receiving and storing means to said threshold by said first current source comprising said cyclic signal.

19. The control system of claim 18 in which said means for changing said initial value comprise means responsive to engine speed, and include:

a second current source for charging said receiving and storing means at a predetermined rate independent of engine speed and different from the charging rate provided by current from said first source; and

switching means for connecting said second current source with said receiving and storing means for only a predetermined portion of each engine cycle and thereafter connecting said first source with said receiving and storing means, the time during which said second source charges said receiving and storing means and thus the value of the summed signal upon initiation of the charging of said receiving and storing means by said first source thereby being determined by engine speed.

20. The control system of claim 19 further including means for preventing the charging of said receiving and storing means during a predetermined portion of each engine cycle to cause variations in engine speed falling within a predetermined range to produce no change in said initial value.

* k t t i 

1. In combination with an internal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of at least one fuel injection valve in response ro the rotation of an engine crank shaft, the improvement wherein said control circuit comprises: means for generating a first pulse train which produces at least one pulse for each revolution of the engine crank shaft, said first pulse train having pulses which begin at an initial point and then increase at a controllable rate; means for varying the magnitude of the initial point at which each of said pulses of said first pulse train begin; means for generating a second pulse train having pulse durations which begin when a pulse from said first pulse train is initiated and end when a pulse from said first pulse train reaches a value established by a sensed engine operating parameter; and means for applying the pulses of said second pulse train to the fuel injector valve to open the valve for the duration of a pulse of said second pulse train.
 2. The combination as recited in claim 1 wherein the means for varying the magnitude of said initial point at which each of said pulses of said first pulse train begins comprises: a ramp generator which establishes a locus of points at which the pulses of said first pulse train are capable of beginning; and means for delaying the generation of said ramp for a predetermined time interval.
 3. In combination with an internal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of at least one fuel injection valve in response to the rotation of an engine crank shaft, the improvement wherein said control circuit comprises: means for generating a first pulse train which produces a pulse for each revolution of the engine crank shaft, said first pulse train having pulses whose magnitudes vary in a predetermined manner; means for generating a second pulse train which produces a pulse for each revolution of the engine crank shaft out of phase by a known phase differential with the pulses of said first pulse train, said second pulse train having pulses whose magnitudes increase at a predetermined rate; means for combining the pulses of said first and second pulse trains so that the beginning of a pulse from said second pulse train terminates a pulse from said first pulse train and the end of a pulse from said second pulse train initiates a pulse from said first pulse train; means for generating a third pulse train having pulses which begin when a pulse from said second pulse train begins and end when a pulse from said second pulse train reaches a predeterminable value; means for applying said third pulse train to the fuel injection valve to open the valve for the duration of a pulse from said third pulse train.
 4. The combination as recited in claim 3 wherein said means for generating a third pulse train includes: means for generating a signal which is a function of an operating parameter of the engine to establish said predeterminable value which when reached by each of said pulse of said second pulse train, terminates a third pulse train pulses.
 5. The combination as recited in claim 4 wherein the duration of a pulse of said first and second pulse train is equal to the time required for the said engine to complete one engine cycle.
 6. In an internal combustion engine fuel control system of the type having triggering means operative to generate triggering signals indicative of the occurrence of engine triggering events, a computing means comprising: at least two current source means operative to generate first and second electrical currents having predeterminable magnitudes; network means, having at least one storage member, for receiving said currents and storing electrical signals in response thereto; first switching means for sequentially applying said currents to said at least one storage member in response to the triggering signals, said first current being applied to said at least one storage member for a period of time immediately following a first triggering signal and said second current being applied to said at least one storage member in response to a selected succeeding triggering signal; and threshold means coupled to said network means responsive to the electrical signal stored therein operative to generate a signal for the period of time following the selected succeeding triggering signal that the stored electrical signal maintains a selected relationship to a threshold value.
 7. The system as claimed in claim 6 wherein said network means comprise: at least two capacitive members and said first switching means are operative to alternating apply each of said first and second currents to said two capacitive members whereby the charge acCumulated on said capacitive members will be a function of the duration of application of each of said first and second currents.
 8. The system as claimed in claim 7 wherein said second current can charge either of said at least two capacitors to a higher voltage.
 9. The system as claimed in claim 7 wherein said at least two capacitors are substantially equal.
 10. The system as claimed in claim 6 including further second switching means responsive to a first triggering event operative to controllably limit the maximum value of electrical signal stored by said storage member.
 11. The system as claimed in claim 10 wherein said second switching means further include means responsive to the time elapsed from said first triggering signal operative to controllably vary the limit established by said second switching means.
 12. The system as claimed by claim 10 wherein the limit value of stored electrical signal is removed upon the occurrence of the selected succeeding triggering event.
 13. In combination with an internal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of an electromagnetically operated fuel injection valve in response to the rotation of said engine crank shaft, the improvement wherein said control circuit comprises: means for generating a first pulse train which produces a pulse for each revolution of said engine crank shaft, said first pulse train having pulses which begin at an initial point and then increase at a constant rate which rate is the same for each of said pulses; means for varying the magnitude of the initial point at which each of said pulses of said first pulse train begin; means for generating a second pulse train having pulse durations which begin when a pulse from said first pulse train is initiated and end when a pulse from said first pulse train reaches a predetermined value established by a sensed engine operating parameter; and means for applying the pulses of said second pulse train to said electromagnetically operated fuel injector valve to open said valve for the duration of each pulse of said second pulse train.
 14. In combination with an internal combustion engine fuel injection control system of the type having a control circuit to electrically control the open time of an electromagnetically operated fuel injection valve in response to the rotation of said engine crank shaft, the improvement wherein said control circuit comprises: means for generating a first pulse train which produces a pulse for each revolution of said engine crank shaft, said first pulse train having pulses whose magnitudes vary in a predetermined manner; means for generating a second pulse train which produces a pulse for each revolution of said engine crank shaft 180* out of phase with the pulses of said first pulse train, said second pulse train having pulses whose magnitudes increase at a constant rate for all pulse durations; means for combining the pulses of said first and second pulse trains so that the beginning of a pulse from said second pulse train terminates a pulse from said first pulse train and the end of a pulse from said second pulse train initiates a pulse from said first pulse train; means for generating a third pulse train having pulses which begin when a pulse from said second pulse train begins and ends when a pulse from said second pulse train reaches a predetermined value; and means for applying said third pulse train to said electromagnetically operated fuel injection valve to open said injector valve for the duration of each pulse from said third pulse train.
 15. A fuel injection control system responsive to at least two variable operating characteristics of an internal combustion engine for controlling the provision of fuel to said engine comprising: means responsive to one of the variable operating characteristics for generating a threshold signal having a value determined by the vaLue of said one variable operating characteristic; means for generating a cyclic signal having a value that varies at a predetermined rate from an initial value to the threshold value at least once during each cycle of engine operation; and means responsive to the other variable operating characteristic for changing said initial value, a change in either the initial or threshold value thereby changing the time required for the cyclic signal to reach the threshold value by an amount that is independent of the magnitude of the other of said values; fuel delivery means responsive to said cyclic signal for providing fuel to the engine for a period in each engine cycle determined by the time required for said cyclic signal to vary from said initial value to said threshold value.
 16. The control system of claim 15 in which: said threshold signal generating means comprise means responsive to engine air consumption; and said means for changing said initial value comprise means responsive to engine speed.
 17. The control system of claim 15 in which said means for generating a cyclic signal comprises means for generating a signal that varies at a fixed rate, a change in either one of said initial or threshold values thereby changing the period of fuel injection by the same amount for all levels of the other of said initial or threshold values.
 18. The control system of claim 15 in which said means for generating said cyclic signal comprise: means for receiving and storing electric signals; a first current source for charging said receiving and storing means to the threshold value; and means for discharging said receiving and storing means at least once for each engine cycle, the charging of said receiving and storing means to said threshold by said first current source comprising said cyclic signal.
 19. The control system of claim 18 in which said means for changing said initial value comprise means responsive to engine speed, and include: a second current source for charging said receiving and storing means at a predetermined rate independent of engine speed and different from the charging rate provided by current from said first source; and switching means for connecting said second current source with said receiving and storing means for only a predetermined portion of each engine cycle and thereafter connecting said first source with said receiving and storing means, the time during which said second source charges said receiving and storing means and thus the value of the summed signal upon initiation of the charging of said receiving and storing means by said first source thereby being determined by engine speed.
 20. The control system of claim 19 further including means for preventing the charging of said receiving and storing means during a predetermined portion of each engine cycle to cause variations in engine speed falling within a predetermined range to produce no change in said initial value. 